Rotating blades in a blade assembly may experience bending, twisting, and aerodynamic forces that can lead to a blade moving out-of-plane with respect to the other blades. Such deviations with respect to the horizontal plane of rotation or other imbalances can undesirably produce vibrations or increase wear on components of the blade assembly, other avionics and airframe components, as well as contribute to crew fatigue.
Many existing approaches used to detect the track height of the blades involve the use of photodiodes or other passive optics to detect changes in the ambient light as the blades traverse the field of view of the optics. However, depending on characteristics of the blades (e.g., the color and/or condition of the paint, the type of material, the angle of attack, and the like) and the current environmental conditions (e.g., weather, ambient lighting for the particular time of day, etc.), such approaches may fail to adequately detect the blades, which, in turn, may result in the craft being grounded (e.g., after major maintenance) until the problem can be resolved and the track height can be obtained. Other approaches are more manually intensive, and typically involve applying reflective material to the undersides or tips of the blades for purposes of detecting the track height and removing the reflective material thereafter, and also are largely dependent upon the experience of the operator in order to collect reliable data. These approaches are more time consuming and may still fail for various reasons (e.g., the reflectivity of the material, the angle of attack, the current environmental conditions, and the like). Thus, what is needed is a means for blade track height detection that is reliable across a wide range of environmental conditions and blade characteristics.